I know gradient boosting use an iteration approach to finding a weak learner. But I am confused about the way to find weak learner,
PDF source
Question 1:
Why find the weak learner by the formula in the blue box
?
Question 2:
What the meaning of the formula $w_ih(\mathbf x_i) $?
Question 3:
In the green box
, I think the formula is to calculate the gradient, but how can I understand -
before the formula?
Thanks for your help!